Calcium movements during E-C coupling in giant muscle fibers from the barnacle will be followed using the aequorin technique. Calcium transients will be quantified either by chemical modification of native aequorin, or by use of calcium sensitive electrodes. The characteristic relationship between voltage clamped membrane potential and the release of calcium from the sarcoplasmic reticulum will be determined. The relationship between calcium level and force will be found using a calcium clamp to control the level of calcium activation. Small length changes will be used to delineate the characteristics of the extra calcium seen during crossbridge cycling. The aequorin technique will be used to investigate the mechanism of sperm activation, and the role of calcium transients during cell division in Medaka eggs.